Tire change.

[nids]

I know this isn't the jeep section but at least I may get a quick response here. I own a Wrangler 98 Sahara (manual) 4.0L. It is fully stock and I wish to upgrade the tires from 29" to 31" (Thornberg's. I also wish to change the differentials from the existing 3.7? to 4.1 so as to compensate for the bigger tire size. I just need to know if changing the diff's is a prudent course of action and if so, what will be the result?

[bluesfool]

It's been quite a while since I've worried about truck stuff, but for what it's worth, here's my 2 cents anyway. How does the jeep run with the 31's now? Is it very sluggish? I would think changing to 4.10 gears would more than compensate for the extra 2" in tire size, meaning the engine will still run faster with the 31's at the same highway speed than with the 3.7 gears and 29" tires. Do you go off road much? If you are in the sand alot, then you probably want to air down the tires to about 10 psi; in which case your 31" tires would resemble your original 29" tires as far as being tall goes. If you do spend alot of time in the sand with the tires aired down, do you really need the high gears then? The 4.10 gears will give you alot of torque while taking away some of your cruising speed capability. How much time do you spend cruising on the highway? It just depends on what you want more; highway speed or low end torgue.

[nids]

Bluesfool, cool name. I hear ya on the torque business. I spend more time on highway but I need extra torque 'cause it's all uphills around here and the extra torque may give me a push up those hills especially when I am trying to overtake. The tires are partly for looks, partly for off-road use and quite a bit to do with the fact that I'm tired of doing spontaneous 360's on a wet or icy road. If you know a better way to increase uphill speed/capability (at relatively high speeds) I'd appreciate a response...supercharger out of the question, will not change engine etc...so I need to make minimal changes and squeeze out maximum results. If anything it's proven to be quite challenging simply because, at the end of the day, we're not dealing with a sports car!

Nids